This invention relates to a master cylinder apparatus chiefly used in a brake apparatus for a motorcar.
In an apparatus of this kind, there has been hereto known arrangements such as, for instance, there shown in FIG. 1, in which a master cylinder c is in communication through a port b with an oil reservior a on its upper side, and is provided therein with a piston f having on its front and rear surfaces respective elastic cups d, e so that the piston f may be pushed to advance against the action of a spring h on its front side by a push rod g.
It has been usual with the prior art arrangement that an oil chamber i on a front side of the piston f communicates with the foregoing upper oil reservoir a through a return port j provided on its rear and upper wall. This conventional arrangement, however, is defective in that on every operation of the piston f, the front elastic cup d slides to move forwardly and rearwardly along on and across the lower end surface of the port j, and thus the cup d is liable to become damaged through co-action with port j.